Wide Bus (4 bit bus width) operation mode may be selected/deselected using ACMD6. The default bus
width after power up or GO_IDLE (CMD0) is 1 bit bus width.
In order to change the bus width two conditions shall be met:
a) The card is in ‘tran state‘ (no data is transferred).
b) The card is not locked
A locked card will responds to ACMD6 as illegal command.